1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) assembly using a surface light source device, and more particularly, to an LCD assembly using a surface light source device which can radiate light at two LCD devices at different luminances.
2. Description of the Related Art
Generally, surface light source devices are used as light sources for light receiving devices. Such light source devices for LCD devices are disclosed in Japanese Patent Publication No. 60-216435 and Korean Patent Publication Nos. 1995-1922, 1996-15030, 1996-24562, and 1994-15029.
For example, a conventional surface light source device includes a light guide plate, a reflection plate fixed on a bottom of the light guide plate, a diffusion plate formed on the light guide plate, and an emitting device, which is implemented by a fluorescent lamp or a light emitting diode (LED), that is fixed on at least one side of the light guide plate. In such a surface light source device, the light guide plate has a structure that scatters and diffuses light on one side of a transparent acryl resin.
Other types of light guide plates include blasting etching types, enplus types, optical insertion (OPI) types, double-sided prism types, and hologram pattern types. Such light guide plates are made by forming scratches on an acryl substrate, in a predetermined pattern, so as to emit light only from one side of the substrate.
Since conventional surface light source devices emit light only from one side, where a stack of two LCD devices is used as in dual type cellular phones, as shown in FIG. 1, surface light source devices 13 and 14 must be installed for LCD devices 11 and 12, respectively. Accordingly, the thickness of the products increases, and thus it is difficult to manufacture thin and light products.
To overcome the above problem, Korean Patent Publication No. 2002-39273 discloses surface light source devices that emit light from both sides thereof. However, such surface light source devices have a problem in that the quantity of light emitted upward cannot be adjusted to be similar to the quantity of light emitted downward. Since the quantity of light emitted upward cannot be actively controlled so as to be different from light emitted downward, an after image of one LCD device smaller than the other LCD device appears on an image of the larger LCD device. Moreover, such conventional surface light source devices have low luminance, and thus there is a limit in increasing the luminance of an image formed by LCD devices.